Cushion for patient interface

ABSTRACT

A cushion for a patient interface that delivers breathable gas to a patient includes a base wall structured to be connected to a frame, an underlying support cushion extending away from the base wall towards the patient&#39;s face in use, and a membrane provided to substantially cover at least a portion of the underlying cushion. The membrane is adapted to form a continuous seal on the patient&#39;s face. The underlying cushion has a spring-like connection with the base wall. The underlying cushion and/or base wall define a spring constant that varies along a length of the seal.

CROSS-REFERENCE TO APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/537,876, filedJun. 29, 2012, pending, which is a continuation of U.S. Ser. No.11/793,981, filed Jun. 25, 2007, now U.S. Pat. No. 8,220,459, which isthe U.S. national phase of international application PCT/AU2006/000032,filed Jan. 12, 2006, which designated the U.S. and claims the benefit ofU.S. Provisional Application Nos. 60/643,130, filed Jan. 12, 2005, and60/724,303, filed Oct. 7, 2005. Each of the applications mentioned aboveis incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a cushion for a patient interface, thepatient interface being used in the treatment, e.g., of Sleep DisorderedBreathing (SDB) with Non-Invasive Positive Pressure Ventilation (NPPV).

BACKGROUND OF THE INVENTION

The use of NPPV for treatment of SDB such as Obstructive Sleep Apnea(OSA) was pioneered by Sullivan (see U.S. Pat. No. 4,944,310). Apparatusfor the treatment of SDB involves a blower which delivers a supply ofair at positive pressure to a patient interface via a conduit. Thepatient interface may take several forms, such as a nasal mask assemblyand a nasal and mouth mask assembly. Patients typically wear a maskassembly while sleeping to receive the NPPV therapy.

Mask assemblies typically comprise a rigid shell or frame and a softface-contacting cushion. The cushion spaces the frame away from thepatient's face. The frame and cushion define a cavity which receives thenose or nose and mouth. The frame and cushion are held in position onthe patient's face by a headgear assembly. The headgear assemblytypically comprises an arrangement of straps which pass along both sidesof the patient's face to the back or crown of the patient's head.

U.S. Pat. No. 5,243,971 (Sullivan and Bruderer) describes a nasal maskassembly for Continuous Positive Airway Pressure (CPAP) having aballooning/molding seal that conforms with the patient's nose and facialcontours. The mask assembly has a face-contacting portion mounted to ashell which is sized and shaped to overfit the nose region of thepatient. The face-contacting portion is in the form of a distendablemembrane which is molded from an elastic plastic material. Thedistendable membrane and the shell together define a chamber.Pressurized gas admitted to the chamber causes the membrane to distendoutwardly from the patient's face. The contents of this patent arehereby incorporated by reference.

U.S. Pat. No. 6,112,746 (Kwok et al.) describes a nasal mask assemblyand a mask cushion therefor. The contents of this patent are herebyincorporated by reference. The cushion comprises a substantiallytriangularly-shaped frame from which extends a membrane. The frame hasan edge by which the cushion is affixed to a mask body. The membrane hasan aperture into which the patient's nose is received. The membrane isspaced away from the rim of the frame, and its outer surface is ofsubstantially the same shape as the rim.

The cushion of a patient interface can play a key role in the comfortand effectiveness of therapy. There is considerable variation in facialsize and shape which can mean that a mask designed for one type of facemay not be suitable for another. For example, an Asian-type nose tendsto have a lower nasal bridge whereas a Caucasian-type nose has a highernasal bridge. Using the wrong cushion can lead to excessive leak anddiscomfort. While creating customized cushions for every patient maysolve some fitting issues, customized masks are very expensive. Thus,manufacturers seek to develop cushions which provide a comfortable andeffective seal for a range of facial sizes and shapes.

SUMMARY OF THE INVENTION

One aspect of the invention is to provide a patient interface having acushion that provides more comfort to the patient while maintaining aneffective seal.

Another aspect of the invention is to provide a comfortable cushion fora patient interface which fits a wide range of facial shapes and sizes.

Another aspect of the invention relates to a cushion including anunderlying cushion and a membrane, wherein the underlying cushion andthe membrane have a substantially flat portion in a nasal region of thecushion.

Another aspect of the invention relates to a cushion including a basewall, an underlying cushion and a membrane, wherein the base wall andunderlying cushion have a cross-sectional configuration that provides avariable spring constant around the perimeter of the cushion.

Another aspect of the invention relates to a patient interface whereinthe base wall and the frame connection of the cushion are internallyoffset with respect to the most external cushion point, e.g., externalmembrane surface.

Another aspect of the invention relates to a cushion including a basewall and underlying cushion that are inclined or angled in a side ofnose region of the cushion.

Another aspect of the invention relates to a cushion having asubstantially constant mouth width irrespective of its face height.

Another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane includes nasalbridge, cheek, and chin regions adapted to form a continuous seal onnasal bridge, cheek, and chin regions of the patient's face,respectively. The nasal bridge region and adjacent two cheek regionsdefine an intersection or apex. The membrane in the nasal bridge regionhas a height at the apex or intersection that is greater than a heightin an adjacent portion of the cheek region.

Another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. The underlying cushion hasa spring-like connection with the base wall. The underlying cushionand/or base wall define a spring constant that varies along a length ofthe seal.

Another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. One of the membrane andthe underlying cushion includes an external surface that defines anouter width of the cushion, and the base wall is internally offset withrespect to the external surface.

Yet another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane includes atleast nasal bridge and side of nose regions adapted to form a continuousseal on nasal bridge and side of nose regions of the patient's face,respectively. The base wall and the underlying cushion in the side ofnose region are inclined or angled with respect to a bottom of theframe.

Yet another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane includes nasalbridge, side of nose, upper cheek, lower cheek and chin regions adaptedto form a continuous seal on nasal bridge, side of nose, upper cheek,lower cheek, and chin regions of the patient's face, respectively. Aninner edge of the membrane defines an aperture that receives thepatient's nose and mouth. A lower portion of the aperture that receivesthe patient's mouth has a mouth width that remains substantiallyconstant irrespective of a face height of the cushion.

Yet another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. At least a portion of theunderlying cushion and/or base wall has a lower portion including aspring configuration that defines displacement of the cushion withrespect to a force applied from the frame.

Still another aspect of the invention relates to a method of designing aseries of mask assemblies. The method includes providing a first cushionadapted to fit a larger range of patients and providing a second cushionadapted to fit a smaller range of patients. Each of the first and secondcushions includes an aperture that receives at least the patient'smouth. The aperture of the first and second cushions have the samewidth.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane includes atleast a nasal bridge region adapted to form a continuous seal on a nasalbridge region of the patient's face. The membrane forms an elongatedridge in the nasal bridge region. The elongated ridge has sloping sidesthat meet to form an elongated crest. Each of the sloping sides isangled from a crest centerline in the range of 30-60° and the crest hasa radius of curvature in the range of 1.0-5.0 mm.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane includes atleast a nasal bridge region adapted to form a continuous seal on a nasalbridge region of the patient's face. The nasal bridge region of themembrane includes a contoured portion that curves inwardly towards acavity of the cushion along a radius to terminate at an inner edge ofthe membrane. The contoured portion has a free end that is angled withrespect to a face contacting plane of the cushion in the range of30-50°.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. The underlying cushionand/or base wall has a question-mark or sickle shape.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. The underlying cushion hasan arcuate configuration including an arc length greater than 16 mm.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame, anunderlying support cushion extending away from the base wall towards thepatient's face in use, and a membrane provided to substantially cover atleast a portion of the underlying cushion. The membrane is adapted toform a continuous seal on the patient's face. The membrane includes athickness that varies along a length of the seal.

Still another aspect of the invention relates to a cushion for a patientinterface that delivers breathable gas to a patient. The cushionincludes a base wall structured to be connected to a frame and amembrane adapted to form a continuous seal on the patient's face. Atleast a portion of the base wall includes a tapered portion that taperstowards the membrane.

Still another aspect of the invention relates to a mask system includinga set of at least two cushions arranged to suit different face sizes,wherein the at least two cushions have substantially the same width.

Other aspects, features, and advantages of this invention will becomeapparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the variousembodiments of this invention. In such drawings:

FIGS. 1-9 illustrate a cushion for a patient interface constructedaccording to an embodiment of the present invention and showingexemplary dimensions of an embodiment;

FIGS. 10-14 are cross-sectional views through the cushion shown in FIG.5;

FIG. 15 is a front view of the cushion shown in FIGS. 1-9 thatillustrates various regions of the cushion;

FIGS. 16-17 illustrates another size of the cushion shown in FIGS. 1-9;

FIGS. 18-19 illustrates yet another size of the cushion shown in FIGS.1-9;

FIGS. 20-21 illustrates still another size of the cushion shown in FIGS.1-9;

FIG. 22 is a cross-sectional view through the cushion shown in FIGS. 1-9that illustrates parameters that can modify a spring characteristic ofthe underlying cushion;

FIGS. 23-29 are cross-sectional views through the cushion shown in FIG.15 and showing exemplary parameters of an embodiment, thecross-sectional views illustrating the underlying cushion only;

FIGS. 30A-30N are cross-sectional views illustrating alternativeembodiments of a cushion according to the present invention;

FIG. 31-32 are graphs illustrating the general relationship betweenForce and Displacement for embodiments of the cushion shown in FIGS. 1-9and a known cushion commercially sold under the name of UltraMirage®Full Face by ResMed Ltd.;

FIG. 33 is a graph illustrating the general relationship between Forceand Displacement for various cross-sections of the cushion shown inFIGS. 23-29;

FIG. 34A illustrates a spring length for the cushion shown in FIGS. 1-9,and showing exemplary dimensions of an embodiment according to thepresent invention;

FIG. 34B illustrates a spring length for a known cushion commerciallysold under the name of UltraMirage® Full Face by ResMed Ltd., andshowing exemplary dimensions of the UltraMirage® Full Face;

FIG. 35 is a side view of the cushion shown in FIGS. 1-9;

FIGS. 36-37 are cross-sectional views through the cushion shown in FIG.35;

FIG. 38 is a front view of the cushion shown in FIGS. 1-9 illustrating aflat portion thereof;

FIG. 38B is a graph illustrating the general relationship between Forceand Displacement in a nasal bridge region for embodiments of the cushionshown in FIGS. 1-9 and a known cushion commercially sold under the nameof UltraMirage® Full Face mask by ResMed Ltd.;

FIGS. 39-40B are front and cross-sectional views of an embodiment of thecushion shown in FIGS. 1-9, and showing exemplary dimensions of anembodiment according to the present invention;

FIGS. 41-45 are perspective views of an embodiment of the cushion shownin FIGS. 1-9 illustrating the rolling action of the nasal bridge regionin use;

FIGS. 46-53 illustrate a known cushion commercially sold under the nameof UltraMirage® Full Face by ResMed Ltd.;

FIGS. 54-58 illustrate a cushion for a patient interface according toanother embodiment of the present invention and showing exemplarydimensions of an embodiment;

FIGS. 59-63 are cross-sectional views through the cushion shown in FIG.54;

FIG. 64 is a cross-sectional view of a portion of the cushion shown inFIGS. 54-58 (in solid lines) overlaid with a cross-section of a knowncushion commercially sold under the name of UltraMirage® Full Face byResMed Ltd. (only relevant portions of the UltraMirage® cushion may beshown in dashed lines, i.e., there may be other different portions notshown);

FIG. 65 is a cross-sectional view of a portion of the cushion shown inFIGS. 54-58 showing exemplary dimensions of an embodiment according tothe present invention;

FIGS. 66-69 are cross-sectional views through the cushion shown in FIG.54, and showing exemplary dimensions of an embodiment according to thepresent invention;

FIGS. 70-71 are plan and cross-sectional views, respectively, of thecushion shown in FIG. 54, and showing exemplary dimensions of anembodiment according to the present invention;

FIGS. 72-76 illustrate a cushion for a patient interface according toanother embodiment of the present invention;

FIGS. 77-83 illustrate a cushion for a patient interface according toanother embodiment of the present invention;

FIGS. 84-90 illustrate a cushion for a patient interface according toanother embodiment of the present invention;

FIG. 91 illustrates an alternative cushion cross-section to that shownin FIG. 34A;

FIG. 92 illustrates another alternative cushion cross-section to thatshown in FIG. 34A;

FIG. 93 illustrates an alternative cushion arrangement to that shown inFIG. 15;

FIGS. 94A-94C are a set of views depicting a horizontal cross-sectionthrough the nasal bridge region of the cushion of FIG. 35; and

FIGS. 95A-95C are a set of views depicting a horizontal cross-sectionthrough the nasal bridge region of the prior art cushion of FIG. 51.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

FIGS. 1-14 illustrate a cushion 10 constructed according to anembodiment of the present invention. The cushion 10 is adapted to beremovably or permanently connected (e.g., via mechanical and/or adhesivefastening) to a frame of a patient interface structured to deliverbreathable gas to a patient. In an embodiment, the cushion 10 may beco-molded to a frame of a patient interface. In another embodiment, thecushion may form part of a frame with an outer support structure, e.g.,ResMed's Hospital Nasal Mask. The cushion 10 provides a seal with thepatient's face during use.

In the illustrated embodiment, the cushion 10 forms a part of afull-face mask. Specifically, the cushion 10 provides a seal around thepatient's nose and mouth to enable the delivery of breathable gas to thepatient's nose and mouth. However, aspects of the present invention maybe applicable to other breathing arrangements, e.g., a nasal mask, amouth mask, etc. The cushion 10 may be used with a gusset as describedin U.S. patent application Ser. No. 10/655,622, incorporated herein byreference in its entirety.

The cushion 10 is structured to provide a more comfortable fit for awide range of facial shapes and sizes. Also, the cushion 10 isstructured to provide a better seal and reduce the risk of leakage asdiscussed below.

As illustrated in FIGS. 1-14, the cushion 10 includes anon-face-contacting portion 12 structured to be connected to a frame ofthe patient interface, e.g., via a friction-fit, a tongue-and-groovearrangement, etc., and a face-contacting portion 14 structured to engagethe patient's face.

As best shown in FIGS. 5 and 15, the face-contacting portion 14 of thecushion 10 preferably has a generally triangular shape and is structuredto continuously contact nasal bridge, side of nose, upper cheek, lowercheek, and chin regions of the patient. However, the face-contactingportion 14 may have other suitable shapes, e.g., a generally trapezoidalshape. In the illustrated embodiment, as best shown in FIG. 15, thecushion 10 includes a nasal bridge region 16 to provide a seal along thepatient's nasal bridge, a pair of cheek regions 15 to provide a sealalong the patient's nose, cheek, and mouth, and a chin region 20 toprovide a seal along the patient's chin. The pair of cheek regions 15may be further defined as a pair of side of nose regions 17 to provide aseal along the sides of the patient's nose, a pair of upper cheekregions 18 to provide a seal along upper cheeks of the patient, and apair of lower cheek regions 19 to provide a seal along the patient'slower cheeks and the sides of the patient's mouth.

Width of Cushion in Lower Cheek Regions and Ratio of Face Width toHeight Across Mask Sizes

The cushion 10 may be provided in various sizes in order to accommodatevarious facial sizes. For example, FIGS. 16-21 illustrate embodiments ofthe cushion 10 in three other sizes. In an embodiment, the cushion 210shown in FIGS. 16-17 may represent a extra small size, the cushion 310shown in FIGS. 18-19 may represent a small size, the cushion 10 shown inFIGS. 1-14 may represent a medium size, and the cushion 410 shown inFIGS. 20-21 may represent a large size. As illustrated, the mouth widthof the cushions 10, 210, 310, 410 are substantially constantirrespective of their face height.

Specifically, the cushion 10 defines an aperture 22 that receives thepatient's mouth. In a preferred embodiment, the lower portion of theaperture 22 has a constant width for all cushion sizes, e.g., 60 mm.However, the width of the lower portion of the aperture 22 may be almostconstant, e.g., in a range of 5 mm, for all cushion sizes. For example,the width of the lower portion of the aperture 22 of the cushion 10 maybe 60 mm±5. In contrast, the width of the lower portion of the aperture722 of a known cushion 700 commercially sold under the name ofUltraMirage® Full Face by ResMed Ltd. is 60 mm for a large size, 54 mmfor a medium size, and 52 mm for a small size. The UltraMirage® cushion700 is shown in FIGS. 46-53.

Anthropometric data has indicated that mouth widths for patients withrelatively small faces are not necessarily narrower than mouth widthsfor patients with relatively large faces. Hence, all faces generallyhave the same mouth width. Thus, the aperture 22 in the cushion 10 ismade sufficiently wide to accommodate a wide range of patients andremains constant or almost constant, e.g., a range of 5 mm, regardlessof the change in face height of a mask to fit larger faces. This can beseen in the substantially constant cushion geometry around the lowercheek and chin regions of the different cushion sizes, and thus thevarying width to height ratios of the different cushion sizes. Forexample, the lower portion of the aperture 22 of each of the cushions10, 210, 310, 410 has substantially the same width.

Base Wall, Underlying Cushions, and Membrane

As best shown in FIGS. 9 and 10-14, the face-contacting portion 14 ofthe cushion 10 includes a base wall 28, a pair of underlying supportcushions 30 extending away from the base wall 28, and a membrane 32provided to substantially cover at least a portion of the underlyingcushions 30 and provide a sealing structure for the face contactingportion 14. The base wall 28 and underlying cushions 30 provide asupport structure for the membrane 32.

As illustrated, the underlying cushions 30 are preferably provided onlateral sides of the base wall 28 only, e.g., in the side of nose, uppercheek, and lower cheek regions 17, 18, 19, although the underlyingcushions 30 could be joined and substantially surround the patient'snose and also the lower lip or chin region. The underlying cushions 30add rigidity to the membrane 32 at the sides of the patient's mouth andcheeks. While it is preferable that the membrane 32 be thinner than theunderlying cushions 30, they could have the same thickness or themembrane could be thicker than the underlying cushion. Also, theelimination of an underlying cushion in the chin region 20 allows thecushion 10 to more deeply engage with the patient's face in this regionwithout subjecting the patient's chin region 20 to excessive pressure.That is, there is no underlying cushion to restrain the movement of themembrane 32 in this region, which may improve the seal in this regionand adjacent regions. Additionally, the elimination of an underlyingcushion in the chin region 20 enables the cushion 10 to accommodate morefacial shapes and provides more flexibility and allows for movement oropening of the mouth.

In the illustrated embodiment, the face-contacting portion 14 of thecushion has a double-walled construction, i.e., membrane 32 andunderlying cushion 30, in the side of nose, upper cheek, and lower cheekregions 17, 18, 19, and a single-walled construction, i.e., membrane 32,in the nasal bridge and chin regions 16, 20 as shown in FIGS. 10-14. Thesingle wall construction at the top and bottom of the cushion 10 helpsto accommodate high landmarks, e.g., pointed chin, by allowing thecenter of the cushion 10 to flex. This flexibility accommodates morepatients with the same cushion. However, the cushion 10 may have anyother suitable construction, e.g., single walled, double walled, triplewalled or more walled construction, in any suitable region of thecushion 10, e.g., cheek, chin, nasal bridge. For example, the underlyingcushion 30 may extend around the entire perimeter of the cushion 10.Also, the underlying cushion 30 could be completely removed.

As shown in FIGS. 10-14, the membrane thickness may vary in thedifferent regions of the cushion 10. As illustrated, the membrane in thenasal bridge region 16 and upper cheek region 18 is 0.3 mm thick whichtransitions to 0.5 mm thickness in the upper cheek region 18 andmaintains this thickness in the lower cheek and chin regions 19, 20.This arrangement provides greater compliance/stretch across the nasalbridge by providing a thinner membrane. This stretch is not required atthe lower regions and here the thicker membrane is less likely tovibrate on the patient face in use.

Internally Offset Base Wall and Frame Connection

Another aspect of the invention relates to the size and configuration ofthe base wall 28, underlying cushion 30, and membrane 32 of the cushion10. FIGS. 48-50 illustrate the base wall 728, underlying cushion 730,and membrane 732 of the UltraMirage® cushion 700. As illustrated, thecushion 10 has a different cross-sectional profile than the UltraMirage®cushion 700.

For example, as best shown in FIGS. 11-13, the base wall 28 and theframe connection 29 are internally offset with respect to the mostexternal cushion point 39, e.g., external surface of membrane orunderlying cushion. In contrast, the base wall 728 and frame connection729 of the UltraMirage® cushion 700 are not offset with respect to themost external cushion point 739 (see FIGS. 48-50). As a result of thisinward movement, the base width of the cushion 10 is narrowed, e.g., byabout 5 mm or 2.5 mm per base, which provides a less obtrusive cushionand saves material which means less weight and cost. Also, the narrowercushion 10 provides less free length for the cushion 10 to bulgeoutwardly in use, thus helping to minimize or eliminate leakage.

As illustrated, a lower portion of the underlying cushion 30 has a morearcuate, e.g., semi-circular, question-mark, sickle-shape, configurationthat defines a space 34 below a lower portion of the underlying cushion30 and adjacent the base wall 28.

In the illustrated embodiment, the widest or most external cushion pointis the external surface of the underlying cushion 30 and the base wall28 and frame attachment 29 are offset internally with respect to this.Thus, by the design of the cushion 10 and in particular the underlyingcushion curvature, the frame is attached at a narrower point and thusthe frame itself is narrower. This arrangement has significantadvantages in terms of the frame weight, perceived bulk, and size. Thisarrangement may also minimize the dead space within the mask which willhelp to reduce CO₂ rebreathing.

Moreover, the space 34 below the underlying cushion 30 allows a greaterrange of movement of the underlying cushion 30 to add more flexibilityto the underlying cushion 30 and hence the membrane 32 in use.Specifically, the space 34 below the underlying cushion 30 enables moredisplacement of the underlying cushion 30 using substantially the samespace restraints as the UltraMirage® cushion 700, for example.Additionally, the space 34 allows more displacement of the underlyingcushion 30 before bottoming out, therefore reducing discomfort. Thus,this arrangement provides a more gradual force, improves comfort, andallows a wider range of patients to achieve seal.

Variable Spring Constant

As illustrated, the underlying cushion 30 has a spring-like connectionwith the base wall 28 such that the underlying cushion 30 can move withrespect to the base wall 28. That is, the underlying cushion 30 ismovable into the space 34 (the underlying cushion 30 is also movableinto the space 33). Thus, a spring force is provided when a frame forceis applied and the underlying cushion 30 is resiliently moved back intoits initial position when the frame force is released. The underlyingcushion 30 and/or base wall 28 may have any suitable spring constant,and the spring constant may be varied anywhere along its length, e.g.,by tapering and/or varying the thickness of the base wall 28, varyingthe thickness of intermediate and/or lower portions of the underlyingcushion 30. Also, the spring-like connection may extend along the wholeunderlying cushion 30 or the spring-like connection may be localized incertain regions such as the cheekbone region.

Thus, a spring characteristic is molded with the base wall 28 andunderlying cushion 30 of the cushion 10 which allows a continuouslyvariable spring constant to be incorporated into the base wall 28 andunderlying cushion 30, e.g., the wall stiffness can be varied at eachcushion region to suit the sealing requirements in each region which mayvary due to the underlying facial structure of the patient.

The spring characteristics of the base wall 28 and underlying cushion 30may be modified by varying a number of characteristics shown in FIG. 22.For example, the spring characteristics may be modified by varying theunderlying cushion height h, the thickness t, the radius r, and theunderlying cushion offset c. It is to be understood that theseparameters are merely exemplary, and other parameters may be varied tomodify the spring characteristics of the base wall 28 and underlyingcushion 30.

FIGS. 23-29 illustrate parameters of an embodiment of the underlyingcushion 30 and base wall 28 to achieve desired spring characteristics.As illustrated, the underlying cushion 30 and base wall 28 is configuredto provide a variable spring constant around the perimeter of thecushion 10. That is, the spring constant of the underlying cushion 30and base wall 28 differs along the side of nose, upper cheek, and lowercheek regions 17, 18, 19. Although specific parameters of the cushion 10are shown in FIGS. 23-29, it is to be understood that these parametersare merely exemplary and other parameters are possible depending onapplication.

In the nasal bridge region 16 (e.g., see FIG. 10), no underlying cushion30 is provided in order to provide high flexibility and the ability toconform to a variety of facial shapes. However, in an embodiment, theremay be an underlying cushion 30 with a very soft spring characteristicin this region.

In the side of nose regions 17 (see FIGS. 23-24), an underlying cushion30 and base wall 28 with a fairly stiff spring characteristic isprovided in order to provide lateral stability to squeeze the side ofthe patient's nose and keep the membrane 32 in contact with theunderlying cushion 30. As illustrated, this arrangement is achieved by arelatively thick underlying cushion, short height, and tight radius. Inan embodiment of the section shown in FIG. 23, h may be 12 mm, r may be5 mm, t may be 2-3 mm, b may be 4 mm, w1 may be 11.5 mm, and w2 may be 8mm. In an embodiment of the section shown in FIG. 24, h may be 14 mm, rmay be 6-7 mm, t may be 2.5 mm, b may be 4 mm, w1 may be 11.5 mm, w2 maybe 9.5 mm, and α may be 22°. It is to be understood that thesedimensions and ranges are merely exemplary and other dimensions andranges are possible depending on application.

Also, as best shown in FIG. 24, the base wall 28 and underlying cushion30 in the side of nose regions 17 have been rotated by about 22 degreeswith respect to the bottom of the frame. That is, the base wall 28 andunderlying cushion 30 are inclined or angled in the side of nose regions17 of the cushion 10. This arrangement further increases the lateralstability and allows the force on the membrane to be appliedperpendicular to the skin surface at the side of the patient's nose.This further helps to keep the membrane 32 in contact with the patient'sskin and prevent any air leaks. In further embodiments, this angle mayvary from 15 to 30 degrees.

In the upper cheek regions 18 (see FIGS. 25-26), the underlying cushion30 and base wall 28 have a stiffness that is less than that provided inthe side of nose regions 17 but stiffer than that provided in the lowercheek regions 19 due to the geometry of the underlying cushion, this isprovided to suit the firmer bone structure of the upper cheeks. In anembodiment of the section shown in FIG. 25, h may be 12-15 mm,preferably 13.5 mm, r may be 5 mm, t may be 2 mm, b may be 3 mm, and w1may be 11.5 mm. In an embodiment of the section shown in FIG. 26, h maybe 12-15 mm, preferably 13.5 mm, r may be 5 mm, t may be 2 mm, b may be3 mm, and w1 may be 11.5 mm. It is to be understood that thesedimensions and ranges are merely exemplary and other dimensions andranges are possible depending on application.

In the lower cheek regions 19 (see FIGS. 27-29), the underlying cushion30 and base wall 28 has a relatively low spring constant. That is, theunderlying cushion 30 in the lower cheek regions 19 is fairly soft sincethe fleshy cheek region of the patient deforms readily to form a sealwith the cushion at relatively low forces. As illustrated, thisarrangement is achieved by a greater height h, larger radii r, and athinner underlying cushion wall. In an embodiment of the section shownin FIG. 27, h may be 14 mm, r1 may be 5 mm, r2 may be 7 mm, t may be1.5-2 mm, b may be 3.5 mm, and w1 may be 11.5 mm. In an embodiment ofthe section shown in FIG. 28, h may be 16.5 mm, r1 may be 6-7 mm, r2 maybe 8 mm, t may be 1.5 mm, b may be 3.5 mm, and w1 may be 11.5 mm. In anembodiment of the section shown in FIG. 29, h may be 17.5 mm, r1 may be6-7 mm, r2 may be 9-10 mm, t may be 1.5 mm, b may be 3.5 mm, and w1 maybe 11.5 mm. It is to be understood that these dimensions and ranges aremerely exemplary and other dimensions and ranges are possible dependingon application.

In the chin region 20 (see FIG. 14), no underlying cushion 30 isprovided, although a very flexible spring region may be used. The chinregion 20 provides an unconstrained membrane region that allows forlateral movement, mouth opening or movement, and a range of facialshapes.

Thus, the cushion 10 may be configured to provide different verticaland/or lateral stiffness in different regions of the cushion. Forexample, the side of nose regions 16, 17 are laterally stiffer than theother regions in order to provide more lateral stability at thepatient's nose.

Alternative Embodiments of Base Wall and Underlying Cushion

FIGS. 30A-30N illustrate alternative embodiments of the base wall 28 andthe underlying cushion 30. Each of these embodiments provides anarrangement that allows flexibility of the underlying cushion 30 in use.In FIG. 30A, the underlying cushion 30 defines an enclosed space 60 thatmay optionally be filled with pressurized air, foam, gel, or elastomericmaterial and adapted to dampen movement of the underlying cushion 30 inuse. In FIG. 30B, the space 34 below the underlying cushion 30 is withinthe interior of the breathing cavity. Also, the underlying cushion 30has an arcuate shape that curves away from the interior of the breathingcavity towards the base wall 28. However, the underlying cushion 30 mayhave any other suitable shape. For example, the underlying cushion 30 inFIG. 30C has a bulbous shape, which may be solid or hollow. In FIG. 30D,the underlying cushion 30 has a general Z-shape. In FIGS. 30E and 30F,the underlying cushion 30 has a bulbous shape (which may be solid orhollow), and the space 34 below the underlying cushion 30 has a rampedconfiguration. In FIGS. 30C, 30E, and 30F, the bulbous shape mayoptionally be filled with pressurized air, foam gel, or elastomericmaterial and adapted to dampen movement of the underlying cushion 30 inuse. In FIG. 30E the ramped configuration of the space 34 is adapted todirect the underlying cushion 30 downwardly into the base wall 28 inuse, and in FIG. 30F the ramped configuration of the space 34 is adaptedto direct the underlying cushion 30 inwardly towards the breathingcavity in use. In FIGS. 30G, 30H, and 30I, the underlying cushion 30 hasa general T-shape. Also, in FIGS. 30H and 30I, the base wall 28 definesan enclosed space 62 below the T-shaped underlying cushion 30. Theenclosed space 62 may be optionally filled with pressurized air, foam,gel, or elastomeric material and adapted to dampen movement of theunderlying cushion 30 in use. Moreover, the spring constant may bevaried by varying the pressure within the enclosed space 62.Additionally, the lower surface of the space 62 may have a rampedconfiguration (as shown in FIG. 30H) adapted to direct the underlyingcushion 30 inwardly towards the breathing cavity in use. The lowersurface of the enclosed space 60 in FIG. 30A may also have a rampedconfiguration for directing the underlying cushion 30 in use. In FIGS.30J and 30K, the underlying cushion 30 has an elongated section lengthfor soft spring characteristics. FIG. 30L illustrates a single wallconstruction with an underlying cushion 30 and no membrane. In FIG. 30M,the space 34 below the underlying cushion 30 is greatly increased. InFIG. 30N, a spring construction is provided below the base wall 28.

Displacement Provided by Underlying Cushion

The space 34 allows more displacement of the underlying cushion 30 for apredetermined amount of force when compared to the UltraMirage® cushion700. That is, the underlying cushion 30 provides more movement for agiven force. For example, FIG. 31 illustrates the general relationshipbetween Force and Displacement for the cushion 10 and the UltraMirage®cushion 700. As illustrated, the curve for the cushion 10 is flatterthan the exponential-type curve of the UltraMirage® cushion 700. Thus,the underlying cushion 30 is less stiff and more compliant when comparedto the UltraMirage® cushion 700. It is noted that the space 34 could befilled with a gel, silicone or other structure to vary the springcharacteristic that it provides.

Further, as illustrated in FIG. 31, the point B₁₀ at which the cushion10 is fully compressed or bottomed-out is at a greater displacement thanthe point B₇₀₀ at which the UltraMirage® cushion 700 is bottomed-out.Moreover, the bottom-out point B₁₀ occurs at a greater force than thebottom-out point B₇₀₀. Thus, the cushion 10 increases the force requiredto bottom-out, and provides a wider range of adjustment. Additionally,FIG. 31 illustrates an example of maximum and minimum comfortablesealing forces, which provides an example force range necessary toachieve seal. As illustrated, the range of displacement A₁₀ within thisforce range for the cushion 10 is substantially larger than the range ofdisplacement A₇₀₀ within this force range for the UltraMirage® cushion700. Thus, the cushion 10 allows a wide range of adjustment ordisplacement to achieve seal, and ensures that the sealing force issubstantially less than the bottom-out force so that the cushion doesnot have to bottom-out to seal.

FIG. 32 illustrates another embodiment of the relationship between Forceand Displacement for the cushion 10 and the UltraMirage® cushion 700. Inthis embodiment, the linear portion of the curve for cushion 10 has agreater slope than the linear portion of the curve for cushion 10 inFIG. 31. The difference in slope may be attributed to a difference inspring constants of respective underlying cushions 30. Thus, the cushionrepresented in FIG. 31 provides more displacement for a given force thanthe cushion represented in FIG. 32. Also, the curve for the cushion 10in FIG. 32 intersects with the curve for the UltraMirage® cushion 700,such that the force of cushion 10 is higher at lower displacement, toensure a seal, and lower at higher displacement, to maintain comfort fora longer range of displacement.

FIG. 33 illustrates another embodiment of the relationship between Forceand Displacement for the cushion 10. In this embodiment, typical curvesfor the different regions of the cushion 10 are shown. Specifically, onecurve represents the cross-sections of FIGS. 23-24 in the side of noseregion 17, another curve represents the cross-sections of FIGS. 25-27 inupper cheek and lower cheek regions 18, 19, and yet another curverepresents the cross-sections of FIGS. 28-29 in the lower cheek region19. As illustrated, the cushion 10 is softer or less stiff in the lowerregions of the cushion 10.

Extended Spring Length of Underlying Cushion

FIGS. 34A and 34B illustrate the extended length of the flexibleunderlying cushion 30 which is used to provide a softer springcharacteristic in selected regions of the cushion 10 when compared witha typical prior art cushion, e.g., the UltraMirage® cushion 700. Thelength a to b can deform, thus providing a spring characteristic. Asillustrated, the length a to b of the cushion 10 (FIG. 34A) isconsiderably longer when compared to the UltraMirage® cushion 700 (FIG.34B) due to the curvature of the underlying cushion 30. In theillustrated embodiment, the length a to b of the cushion 10 is 22.84.However, in an embodiment, the length a to b of the cushion 10 may be inthe range of 16-30, preferably 20-25, most preferably 22-24. In anotherembodiment, the length a to b of the cushion 10 may be in the range of16-20. The length b to c is fairly rigid and does not deform to providea spring characteristic. The added length in the cushion 10 has beenachieved by the arcuate shape of the underlying cushion 30 and the space34 is a result of this shape. This added length adds flexibility and agreater range of movement to the cushion 10. FIGS. 30J and 30Killustrate other embodiments for achieving a longer section length.

Configuration of Membrane in Nasal Bridge Region

The membrane 32 is structured to form an effective seal around nasalbridge, side of nose, upper cheek, lower cheek, and chin regions 16, 17,18, 19, 20 of a patient. Another aspect of the invention relates to theconfiguration of the membrane 32 in the nasal bridge region 16 of thecushion 10, which has been structured to improve sealing and comfort inthis region.

Specifically, as shown in a preferred embodiment in FIG. 36 and in analternative embodiment in FIG. 68, the membrane 32 forms an elongatedridge 35 in the nasal bridge region 16 wherein sloping sides 36 meet toform an elongated crest 38. Each of the sloping sides 36 is angled fromthe crest centerline in the range of 30-60°, preferably about 47°. Thecrest 38 has a radius of curvature in the range of 1.0-5.0 mm,preferably about 2.5 mm. As illustrated, the underlying cushion 30 hasbeen eliminated from beneath the membrane 32 in the nasal bridge region16, which allows the membrane 32 in this region to freely move betweenthe underlying cushions 30 provided in the side of nose regions 17. Asdiscussed in greater detail below, this membrane configuration allowsthe creation of a steeply inverted section upon engagement with thepatient's nose, which improves fit, comfort, and seal in the nasalbridge region 16. In contrast, the UltraMirage® cushion 700 isrelatively flat in this region (see FIG. 52).

As shown in a preferred embodiment in FIG. 37 and in an alternativeembodiment in FIG. 69, the forward end 40 of the elongated ridge 35 hasan arcuate configuration. The forward end 40 is structured to engage thepatient's nasal bridge region and has a radius of curvature in the rangeof 1.5-7.0 mm, preferably about 4.0 mm.

Sharp Cross-Sectional Profile of Nasal Bridge Region

As shown in FIG. 10, the membrane 32 in the nasal bridge region 16 has asharper cross-sectional profile than the corresponding portion of theUltraMirage® cushion 700 (see FIG. 48). Specifically, the membrane 32provides a large contoured portion that curves inwardly towards thecavity of the cushion along a radius to terminate at an inner edge ofthe membrane 32. This arrangement more closely follows the contour orcurvature of the patient's nasal bridge region. In the illustratedembodiment, the membrane 32 is angled with respect to a face contactingplane of the cushion, e.g., in the range of 30-50°. In contrast, thecorresponding angle of the UltraMirage® cushion 700 is about 6°. Thisarrangement provides more comfort and a better fit for the patient.

Flat Portion in Nasal Bridge Region

As best shown in FIG. 38, the nasal bridge region 16 has a substantiallyflat portion 50, e.g., on the apex of the membrane curvature, inelevation view that may deform to provide a more comfortable fit for awide range of patients, e.g., from flatter nasal bridges to sharpernasal bridges.

Specifically, one aspect of the invention is to provide a membrane 32 inthe nasal bridge region 16 that will accommodate “flat faces”, e.g.,those patient's with a low nasal bridge. In order to achieve this, thecushion 10 has an upper point A which is higher than or level withpoints B (see FIG. 38). This height in the nasal bridge region 16 iscombined with a rolled edge that keeps the surface area of the membrane36 substantially flat against the patient's nasal bridge. Keeping thesurface area of the membrane 36 substantially flat against the patient'snasal bridge prevents leaks at the edge of the membrane.

The rolled edge also allows movement to accommodate higher nasalbridges. This arrangement is achieved without “stretching” the membranewhich can lead to discomfort and patient sores. For example, thedisplacement of the cushion 10 at the nasal bridge region 16 may begreater than about 40 mm, e.g., 41 mm. In contrast, the UltraMirage®cushion 700 provides displacement of about 20 mm in the nasal bridgeregion. At these displacements, the membrane becomes quite taut, i.e.,the point on the force vs. displacement graph where the force begins torise sharply for a small displacement (see FIG. 38B).

The displacement values of the cushion in the nasal bridge region forsome prior art cushions are as follows:

ResMed™ Activa® Nasal Cushion—16 mm

Respironics Comfort Full Face Cushion—26 mm

ResMed Bubble Nasal Mask Cushion—43 mm

Healthdyne Soft Series Nasal Mask Cushion—17 mm

The above displacement values are by no means an accurate representationof what nose depth the cushion will cover. Rather, these displacementvalues are only an indication of the flexibility and/or range of themembrane. Thus, the cushion 10 provides an arrangement that is much moreflexible and/or rangy than the UltraMirage® cushion 700, for example.

The force vs. displacement graph of membrane 32 in the nasal bridgeregion 16 has a large displacement for relatively low forces. Forexample, as shown in FIG. 38B, the displacement provided by the cushion10 in the nasal bridge region 16 is larger than that provided by theUltraMirage® cushion 700. This allows the cushion 10 to accommodaterelatively deep nasal bridges in use. Also, the molded (undeformed)cushion state of the UltraMirage® cushion 700 (i.e., no force applied)does not comfortably accommodate a relatively flat or shallow nasalbridge. In an embodiment, the membrane of the cushion 700 blows out tomeet patient's faces with shallow nasal bridges. Thus, the cushion 10also accommodates a wider range of nasal bridge shapes than theUltraMirage® cushion 700.

Further, as shown in FIG. 36, the profile of the membrane is moresharply peaked as compared to a flat profile or a saddle shape (e.g.,compare with UltraMirage® cushion 700 in FIG. 52). Also, as shown inFIG. 35, flat portion in the nasal bridge region 16 extends along arelatively flat plane P1, and this plane P1 is angled at an angle A withrespect to the plane P2 that defines the frame connection.

Thus, the shape (e.g., peak), the rolled edge, and the height, in thenasal bridge region 16 provide large displacement at relatively lowforces. This arrangement accommodates a wider range of patients, e.g.,from those with a low nasal bridge to those with a high nasal bridge,while maintaining a seal against the patient's face with little force onthe membrane.

It is noted that the cushion height may vary around the cushionperimeter to vary flexibility or cushion displacement in differentregions of the cushion. A reference dimension 940 for measurement of thecushion height (which may also be referred to as the membraneheight)—i.e. the height between the apex of the membrane to where itmeets the underlying cushion—is shown in FIG. 94C. A reference dimension950 for measurement of the cushion height of the prior art cushion isshown in FIG. 95C.

Aperture in Membrane

As shown in FIGS. 39-40B, the inner edge of the membrane 32 defines theaperture 22 that receives the patient's nose and mouth. As illustrated,the aperture 22 has a generally triangular shape. Also, the apex of theaperture 22 has a rounded notch 42, e.g., keyhole. The notch 42 improvesthe seal with nasal bridge regions of various sizes and shapes,particularly patients with sharp noses. The notch 42 has a radius ofcurvature in the range of 1.5-6.0 mm, preferably about 3.0 mm. Thisrounded keyhole shape has a length, e.g., the keyhole shape extendsoutwards from an interior portion of the cushion, of at least 3.0 mm, asshown in FIG. 40A.

Rolling Action of Nasal Bridge Region of Cushion in Use

FIGS. 41-45 include hand-marked lines applied to the outer surface ofthe nasal bridge region 16 of the cushion 10 to illustrate the rollingaction of the nasal bridge region 16 of the membrane 32 upon engagementwith the patient's nose. As described above, the membrane 32 in thenasal bridge region 16 includes sloping sides 36 that meet to form anelongated crest 38 as shown in FIG. 41. As the patient's nasal bridge(simulated using a small rod) is engaged with the nasal bridge region 16of the membrane 32 (see FIG. 42), the membrane 32 creates a steeplyinverted section 44 wherein the sloping sides 36 invert their positionas the membrane 32 moves between the underlying cushions 30 provided inthe side of nose regions 17. As the membrane 32 comes more into contactwith the patient's nasal bridge, the leading edge 46 of the invertedsection “rolls” towards the top of the cushion 10 as the membrane 32conforms to the patient's face as shown in FIG. 43. This structure isadvantageous since it allows the cushion 10 to accommodate patientshaving a wide range of nasal profiles, including those with relativelylow and relatively high root depth at the nose. FIGS. 44 and 45 show thenasal bridge region 16 of the membrane 32 in its completely invertedposition. The creation of the steeply inverted section 44 uponengagement with the patient's nose provides a better seal and reducesthe risk of creasing and/or folding and associated discomfort and leaks.That is, this configuration encourages rolling instead of creasing whichcan be detrimental to patient comfort and seal.

Alternative Embodiments

FIGS. 54-71 illustrate another embodiment of a cushion 510. In each ofthe figures, portions of the cushion 510 that are substantially similarto the cushion 10 are indicated with similar reference numerals.

FIG. 64 illustrates the base wall 528, underlying cushion 530, andmembrane 532 of the cushion 510 (in solid lines) in relation to the basewall 728, underlying cushion 730, and membrane 732 of the UltraMirage®Full Face cushion 700 (in dashed lines). As illustrated, the cushion 510has a different cross-sectional profile than the UltraMirage® Full Facecushion 700.

For example, the membrane 532 is connected to the underlying cushion 530at a position that is further inwardly and upwardly with respect to themembrane connection of the UltraMirage® cushion 700. This arrangementsubstantially removes the vertically extending groove 731 provided inthe UltraMirage® cushion 700. Also, this arrangement narrows the widthof the membrane 532, e.g., in the range of 0-5, preferably about 2.5 mm,with respect to the corresponding portion of the UltraMirage® cushion700. As a result of this and the inward movement of the non-facecontacting portion 512, this narrows the total width of the cushion 510by about 5 mm, e.g., about 2.5 mm per base, which provides a lessobtrusive cushion and saves material. Also, the narrower membrane 532provides less free length for the cushion 510 to bulge outwardly in use,thus helping to minimize or eliminate leakage. Further, the base wall528 and the frame connection 529 are internally offset with respect tothe most external cushion point, e.g., external surface of underlyingcushion. FIG. 64 also shows the longer length a to b in the cushion 510when compared to the UltraMirage® cushion 700.

FIG. 65 illustrates further structural details and dimensions in oneembodiment of the base wall 528, underlying cushion 530, and membrane532 of the cushion 510. For example, the depth of the space 534 is inthe range of 0-4.0 mm, preferably about 3.0 mm.

FIG. 68 illustrates the elongated ridge 535 in the nasal bridge region516. Each of the sloping sides 536 is angled from the crest centerlinein the range of 30-60°, preferably about 47°. The crest 538 has a radiusof curvature in the range of 1.0-5.0 mm, preferably about 2.5 mm. Asshown in FIG. 69, the forward end 540 of the elongated ridge 535 has aradius of curvature in the range of 1.5-7.0 mm, preferably about 4.0 mm.

FIGS. 70 and 71 illustrate the flat portion 550 in the nasal bridgeregion 516 of the cushion 510. Also, as shown in FIG. 71, the membrane532 in the nasal bridge region 516 has a first portion with a radius ofcurvature in the range of 50-80 mm, preferably about 65 mm, and a secondportion with a radius of curvature in the range of 5.5-9.5 mm,preferably about 7.5 mm. In the illustrated embodiment, the membrane 532is angled with respect to a face contacting plane of the cushion in therange of 30-50°, preferably about 40°.

FIGS. 72-76 illustrate another embodiment of a cushion 610. As bestshown in FIG. 76, the cushion includes at least a base wall 628 and amembrane 632. As illustrated, the length of the membrane 632 (e.g.,membrane cross-sectional length) in a nasal bridge region may change.For example, the membrane length may be selected to have a shorterlength L₁ or a longer length L₂ in the nasal bridge region.

As shown in FIGS. 74 and 75, the membrane length controls how far on thepatient's nose the displaced cushion membrane will sit when fitted ontothe patient's face (shown by the dotted line on the patient's facialprofile). This arrangement prevents the potential (e.g., particularlyfor patients with a shallow nasal bridge depth) for any excess cushionmembrane to sit too far down on the patient's nose, which may lead tofacial discomfort and skin markings on the patient's nose.

FIGS. 77-83 illustrate another embodiment of a cushion 810. The cushion810 includes a base wall 828, an underlying support cushion 830, and amembrane 832. As described above, the underlying cushion 830 ispreferably provided on lateral sides of the cushion 810 only.

The base wall 828 may be internally offset with respect to the mostexternal cushion point, e.g., external surface of membrane or underlyingcushion. This arrangement provides a spring characteristic which may bevaried around the cushion perimeter to vary the cushion flexibility(lateral and/or vertical) around the cushion perimeter, e.g., thecushion stiffness can be varied at each cushion region to suit thesealing requirements in each region which may vary due to the underlyingfacial structure of the patient. That is, the level if bias (e.g., from“hard” to “soft”) along the sides of the cushion may be changed.

For example, FIGS. 77-83 illustrate cross-sections through threedifferent regions R1, R2, R3 in the cushion 810. As shown in FIG. 81,the base wall 828, the underlying cushion 830, and the membrane 832cooperate to define a relatively straight external surface 880. Thisprovides a minimal spring component in the region R1, e.g., hard orstiff characteristics.

As shown in FIG. 82, the base wall 828, the underlying cushion 830, andthe membrane 832 cooperate to define an external surface 882 thattransitions from a relatively straight configuration to a curvedconfiguration. This provides a relatively small offset for a moreflexible spring component than the region R1.

As shown in FIG. 83, the base wall 828, the underlying cushion 830, andthe membrane 832 cooperate to define an external surface 884 that curvesoutwards from the base wall 828. This provides a relatively large offsetfor an optimal spring component in the region R3, e.g., soft or flexiblecharacteristics.

Thus, the cushion 810 may be designed to provide varying flexibilitiesaround its perimeter which allows the cushion 810 to conform to avariety of facial shapes.

FIGS. 84-90 illustrate another embodiment of a cushion 910. The cushion910 includes a base wall 928, an underlying support cushion 930, and amembrane 932. As illustrated, the underlying cushion 930 is preferablyprovided on lateral sides of the cushion 910 only, e.g., no underlyingcushion at nasal bridge and chin regions (see FIG. 88).

As shown in FIG. 90, the base wall 928 includes a tapered portion 990when compared to FIG. 89, which tapers towards the membrane 932. Thisarrangement may improve moldability.

FIG. 91 illustrates an alternative arrangement to the cushion 10 of FIG.34A (arrangement of FIG. 34A shown in dashed lines). As illustrated,material has been removed from the side wall 28 and the space or gap 34has been reduced with respect to the arrangement of FIG. 34A. Thisarrangement of FIG. 91 increases displacement with respect to theprevious displacement of FIG. 34A. The increased displacement isachieved by the changed geometry in the side wall 28. It is noted thatthe gap 34 may be variable or constant around the cushion perimeter.

FIG. 92 illustrates an alternative arrangement to the cushion 10 of FIG.34A (arrangement of FIG. 34A shown in dashed lines). As illustrated,some material has been removed from the side wall 28 and the space orgap 34 has been reduced with respect to the arrangement of FIG. 34A.This arrangement of FIG. 92 increases displacement with respect to theprevious displacement of FIG. 34A. The increased displacement isachieved by the changed geometry in the side wall 28. This arrangementmay require the cross-section of the base wall 28 to be thickened to addstiffness around the cushion perimeter or locally. Stiffening may beachieved by local ribs where required.

FIG. 93 illustrates an alternative arrangement to the cushion 10 shownin FIG. 15. As illustrated, the keyhole-shaped cutout (for receiving thepatient's nasal bridge region) may be larger as the mask size reduces.For example, the cutout is larger for an extra small size mask than alarge size mask.

It is noted that the cross-section design of the cushion at specificareas of the patient's face (e.g., FIGS. 23-29) may be in the specificarea or any area around the cushion perimeter. That is, thecross-section design should not be limited to the specified area. Also,the cross-section shown in FIGS. 91 and 92 may be employed at any pointaround the cushion perimeter.

While the invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention. Also, the various embodiments described abovemay be implemented in conjunction with other embodiments, e.g., aspectsof one embodiment may be combined with aspects of another embodiment torealize yet other embodiments. In addition, while the invention hasparticular application to patients who suffer from OSA, it is to beappreciated that patients who suffer from other illnesses (e.g.,congestive heart failure, diabetes, morbid obesity, stroke, barriatricsurgery, etc.) can derive benefit from the above teachings. Moreover,the above teachings have applicability with patients and non-patientsalike in non-medical applications.

What is claimed is:
 1. A method of selecting a cushion from a series of full-face cushions to deliver breathable gas to a patient via a mask system for treatment of Obstructive Sleep Apnea with Non-Invasive Positive Pressure Ventilation, the method comprising: providing a series of full-face cushions, each of the full-face cushions including a nasal bridge region, cheek regions and a chin region, each of the full-face cushions defining, at least in part, a breathing cavity, the series comprising: a first full-face cushion, the first full-face cushion comprising a first membrane including a first nasal bridge region, first cheek regions and a first chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the first membrane having an inner edge that defines a first triangular-shaped aperture to receive the patient's nose and mouth, the first triangular-shaped aperture including a lower portion having a first mouth width; a second full-face cushion, the second full-face cushion comprising a second membrane including a second nasal bridge region, second cheek regions and a second chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the second membrane having an inner edge that defines a second triangular-shaped aperture to receive the patient's nose and mouth, the second triangular-shaped aperture including a lower portion having a second mouth width; a third full-face cushion, the third full-face cushion comprising a third membrane including a third nasal bridge region, third cheek regions and a third chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the third membrane having an inner edge that defines a third triangular-shaped aperture to receive the patient's nose and mouth, the third triangular-shaped aperture including a lower portion having a third mouth width; and a fourth full-face cushion, the fourth full-face cushion comprising a fourth membrane including a fourth nasal bridge region, fourth cheek regions and a fourth chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the fourth membrane having an inner edge that defines a fourth triangular-shaped aperture to receive the patient's nose and mouth, the fourth triangular-shaped aperture including a lower portion having a fourth mouth width, wherein each of the first, second, third and fourth triangular-shaped apertures has a different height, the first mouth width is within 5 mm of the second, third and fourth mouth widths, the second mouth width is within 5 mm of the third and fourth mouth widths, and the third mouth width is within 5 mm of the fourth mouth width, and selecting, for the treatment, a full-face cushion from the series of full-face cushions, in accordance with a size of the patient's face.
 2. The method of claim 1, wherein each of the first, second, third and fourth full-face cushions includes a support structure, each support structure including: a wall; and an underlying cushion connected to the wall, wherein each underlying cushion, in a cross-sectional view, extends from a respective wall and toward a respective breathing cavity to provide support to a respective one of the first, second, third and fourth membranes, each underlying cushion includes cheek regions extending adjacent a perimeter of a respective one of the first, second, third and fourth triangular-shaped apertures such that each respective full-face cushion has at least a double-walled construction in the cheek regions such that each underlying cushion is positioned to restrain movement of a respective one of the first, second, third and fourth membranes, and each respective full-face cushion has only a single-walled construction in at least a portion of the chin region so as to allow each respective membrane to readily flex in said at least a portion of the chin region.
 3. The method of claim 2, wherein each wall has a top portion and a bottom portion, each of the first, second, third and fourth membranes or each respective support structure forms a widest point of the respective full-face cushion, and the bottom portion of each wall is internally offset with respect to the widest point of the respective full-face cushion.
 4. The method of claim 3, wherein a first cross-sectional configuration of the support structure in the nasal bridge region of each full-face cushion is different than a second cross-sectional configuration of the support structure in the cheek regions of the respective full-face cushion.
 5. The method of claim 4, wherein the first and second cross-sectional configurations of the support structure in the nasal bridge region and the cheek regions of each respective full-face cushion vary by varying an underlying cushion offset.
 6. The method of claim 5, wherein a first portion of each support structure extends laterally beyond a second exterior portion of a respective one of the first, second, third and fourth full-face cushions, and wherein: the first portion of each support structure is movable with respect to the respective second exterior portion when the respective full-face cushion is worn and a force is exerted on the respective full-face cushion, the first portion of each support structure is movable from an initial position towards a space exterior of the respective full-face cushion when the force is applied, and the first portion of each support structure is configured to resiliently move back into the initial position when the force is no longer exerted on the respective full-face cushion.
 7. The method of claim 6, wherein each of the first, second, third and fourth full-face cushions is adapted to exert a spring force when the force is applied such that the first portion of each support structure is configured to resiliently move back into the initial position when the force is no longer exerted on the respective full-face cushion, and wherein at least a portion of each support structure has a variable spring characteristic around a perimeter of the respective full-face cushion.
 8. The method of claim 7, wherein the first and second cross-sectional configurations of each support structure vary from one another so as to provide a spring constant in the nasal bridge region of each respective full-face cushion that is different than a spring constant in the cheek regions of the respective full-face cushion.
 9. The method of claim 8, wherein each of the first, second, third and fourth full-face cushions is dimensioned to fit respective first, second, third and fourth ranges of the patients, the mouth widths of the first, second, third and fourth triangular-shaped apertures are at a widest point of the first, second, third and fourth triangular-shaped apertures, and the height of each of the first, second, third and fourth triangular-shaped apertures is at a tallest point of the first, second, third and fourth triangular-shaped apertures, and wherein the first full-face cushion is a large size full-face cushion, the second full-face cushion is a medium size full-face cushion, the third full-face cushion is a small size full-face cushion and the fourth full-face cushion is a size that is smaller than the third full-face cushion.
 10. The method of claim 9, wherein the first, second and third mouth widths are substantially constant.
 11. The method of claim 10, wherein the first, second, third and fourth mouth widths are substantially constant.
 12. The method of claim 11, wherein each of the first, second, third and fourth membranes has a height in the nasal bridge region of a respective one of the first, second, third and fourth full-face cushions that is greater than a height of the respective membrane in the cheek regions of the respective full-face cushion.
 13. A method of selecting a cushion from a series of full-face cushions to deliver breathable gas to a patient via a mask system for treatment of Obstructive Sleep Apnea with Non-Invasive Positive Pressure Ventilation, the method comprising: providing a series of full-face cushions, each of the full-face cushions including a nasal bridge region, cheek regions and a chin region, each of the full-face cushions defining, at least in part, a breathing cavity, the series comprising: a first full-face cushion, the first full-face cushion comprising a first membrane including a first nasal bridge region, first cheek regions and a first chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the first membrane having an inner edge that defines a first triangular-shaped aperture to receive the patient's nose and mouth, the first triangular-shaped aperture including a lower portion having a first mouth width; and a second full-face cushion, the second full-face cushion comprising a second membrane including a second nasal bridge region, second cheek regions and a second chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the second membrane having an inner edge that defines a second triangular-shaped aperture to receive the patient's nose and mouth, the second triangular-shaped aperture including a lower portion having a second mouth width; wherein a height of the first triangular-shaped aperture is different than a height of the second triangular-shaped aperture, and the first mouth width and the second mouth width are substantially constant, and selecting, for the treatment, a full-face cushion from the series of full-face cushions, in accordance with a size of the patient's face.
 14. The method of claim 13, wherein the series of full-face cushions further comprises a third full-face cushion, the third full-face cushion comprising a third membrane including a third nasal bridge region, third cheek regions and a third chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the third membrane having an inner edge that defines a third triangular-shaped aperture to receive the patient's nose and mouth, the third triangular-shaped aperture including a lower portion having a third mouth width, wherein a height of the third triangular-shaped aperture is different than the heights of the first and second triangular-shaped apertures, and the third mouth width is within 5 mm of the first and second mouth widths.
 15. The method of claim 14, wherein the series of full-face cushions further comprises a fourth full-face cushion, the fourth full-face cushion comprising a fourth membrane including a fourth nasal bridge region, fourth cheek regions and a fourth chin region to seal on a nasal bridge region, cheek regions, and a chin region of the patient's face, the fourth membrane having an inner edge that defines a fourth triangular-shaped aperture to receive the patient's nose and mouth, the fourth triangular-shaped aperture including a lower portion having a fourth mouth width, wherein a height of the fourth triangular-shaped aperture is different than the heights of the first, second and third triangular-shaped apertures, and the fourth mouth width is within 5 mm of the first, second and third mouth widths.
 16. The method of claim 15, wherein each of the first, second, third and fourth full-face cushions includes a support structure, each support structure including: a wall; and an underlying cushion connected to the wall, wherein each underlying cushion, in a cross-sectional view, extends from a respective wall and toward a respective breathing cavity to provide support to a respective one of the first, second, third and fourth membranes, each underlying cushion includes cheek regions extending adjacent a perimeter of a respective one of the first, second, third and fourth triangular-shaped apertures such that each respective full-face cushion has at least a double-walled construction in the cheek regions such that each underlying cushion is positioned to restrain movement of a respective one of the first, second, third and fourth membranes, and each respective full-face cushion has only a single-walled construction in at least a portion of the chin region so as to allow each respective membrane to readily flex in said at least a portion of the chin region.
 17. The method of claim 16, wherein each wall has a top portion and a bottom portion, each of the first, second, third and fourth membranes or each respective support structure forms a widest point of the respective full-face cushion, and the bottom portion of each wall is internally offset with respect to the widest point of the respective full-face cushion.
 18. The method of claim 17, wherein each of the first, second, third and fourth full-face cushions is adapted to exert a spring force when the respective full-face cushion is worn and a force is applied to the respective full-face cushion, such that a first portion of each support structure is configured to resiliently move back into an initial position when the force is no longer exerted on the respective full-face cushion, and wherein at least a portion of each support structure has a variable spring characteristic around a perimeter of the respective full-face cushion.
 19. The method of claim 18, wherein a cross-sectional configuration of the support structure in a first region of each respective full-face cushion varies from a cross-sectional configuration of the support structure in a second region of the respective full-face cushion so as to provide a spring constant in the first region of the respective full-face cushion that is different than a spring constant in the second region of the respective full-face cushion.
 20. The method of claim 19, wherein a first cross-sectional configuration of the support structure in the nasal bridge region of each full-face cushion is different than a second cross-sectional configuration of the support structure in the cheek regions of the respective full-face cushion.
 21. The method of claim 20, wherein a third cross-sectional configuration of the support structure in a lower facial area of the cheek regions of each full-face cushion is different than a fourth cross-sectional configuration of the support structure in an upper facial area of the cheek regions of the respective full-face cushion.
 22. The method of claim 21, wherein the first and second cross-sectional configurations of the support structure in the nasal bridge region and the cheek regions of each respective full-face cushion vary by varying an underlying cushion offset.
 23. The method of claim 22, wherein each of the first, second, third and fourth full-face cushions is dimensioned to fit respective first, second, third and fourth ranges of the patients, the mouth widths of the first, second, third and fourth triangular-shaped apertures are at a widest point of the first, second, third and fourth triangular-shaped apertures, and the height of each of the first, second, third and fourth triangular-shaped apertures is at a tallest point of the first, second, third and fourth triangular-shaped apertures, and wherein the first full-face cushion is a large size full-face cushion, the second full-face cushion is a medium size full-face cushion, the third full-face cushion is a small size full-face cushion and the fourth full-face cushion is a size that is smaller than the third full-face cushion.
 24. The method of claim 23, wherein each underlying cushion includes a nasal bridge region such that each underlying cushion is continuous along the cheek regions and the nasal bridge region of each underlying cushion.
 25. The method of claim 24, wherein each of the first, second, third and fourth membranes has a height in the nasal bridge region of a respective one of the first, second, third and fourth full-face cushions that is greater than a height of the respective membrane in the cheek regions of the respective full-face cushion.
 26. The method of claim 25, wherein the first, second and third mouth widths are substantially constant.
 27. The method of claim 26, wherein the first, second, third and fourth mouth widths are substantially constant.
 28. The method of claim 27, wherein a first portion of each support structure extends laterally beyond a second exterior portion of a respective one of the first, second, third and fourth full-face cushions, wherein: the first portion of each support structure is movable with respect to the respective second exterior portion when the respective full-face cushion is worn and a force is exerted on the respective full-face cushion, the first portion of each support structure is movable from an initial position towards a space exterior of the respective full-face cushion when the force is applied, and the first portion of each support structure is configured to resiliently move back into the initial position when the force is no longer exerted on the respective full-face cushion, wherein at least a portion of each underlying cushion forms the respective first portion of each support structure, and a respective one of the first, second, third and fourth membranes extends from each underlying cushion, and wherein each underlying cushion includes a nasal bridge region such that each underlying cushion is continuous along the cheek regions and the nasal bridge region of the respective underlying cushion.
 29. The method of claim 27, wherein a first portion of each support structure extends laterally beyond a second exterior portion of a respective one of the first, second, third and fourth full-face cushions, wherein: the first portion of each support structure is movable with respect to the respective second exterior portion when the respective full-face cushion is worn and a force is exerted on the respective full-face cushion, the first portion of each support structure is movable from an initial position towards a space exterior of the respective full-face cushion when the force is applied, and the first portion of each support structure is configured to resiliently move back into the initial position when the force is no longer exerted on the respective full-face cushion, wherein at least a portion of each wall forms the respective first portion of each support structure, and a respective one of the first, second, third and fourth membranes extends from each the wall, and wherein each underlying cushion includes a nasal bridge region such that each underlying cushion is continuous along the cheek regions and the nasal bridge region of the respective underlying cushion.
 30. The method of claim 13, wherein each of the first and second full-face cushions is dimensioned to fit respective first and second ranges of the patients, and wherein the first full-face cushion is a large size full-face cushion, and the second full-face cushion is a medium size full-face cushion. 